1. Field of the Invention
The present invention relates generally to irrigation devices, and more particularly to controlling the charging of an energy reserve of an irrigation device.
2. Discussion of the Related Art
Typical irrigation control systems cooperate with water valves and pumps to control the flow of irrigation water through a variety of water dispensing devices, including sprinklers, rotors, drip-lines, and other water delivery devices. These control systems are used in a wide variety of irrigation applications, from residential and commercial landscapes to golf course and agricultural irrigation. Rotors, for example, irrigate by throwing a jet or spray of water that is rotated about a generally vertical axis. Rotors are supplied with water from water supply lines that are usually installed below ground and are typically actuated by electric solenoid-controlled valves powered by an energy reserve.
A two-wire irrigation control system allows for the control of many remote devices each coupled at different locations in the field to a single two-wire transmission line called a two-wire interface extending through the field. An interface controller transmits alternating power signals, such as 50/60 Hz AC voltage signals, along the two-wire interface. The interface controller also modulates data on the alternating power signal, for example, by selectively clipping the positive half of the power signal. The remote devices derive their operational power from the received signaling and demodulate the data from the power signal. In this way, the interface controller can address one or more remote devices and send irrigation commands thereto. Such systems allow for the control of tens to hundreds of remote devices coupled to the single two-wire interface and are well known in the art and described, for example in U.S. Pat. No. 4,176,395 to Evelyn-Veere. A typical remote device controls the operation of a water flow control valve. A system initialization operation is commonly performed after installing irrigation devices or as part of system or ongoing, periodic field maintenance operations. During this initialization process, a large number of remote irrigation devices will undergo power-up within a short period of time. Powering-up the remote irrigation devices typically requires charging their respective energy reserves in order to power the microcontroller of the remote irrigation device and for powering an associated solenoid (e.g., to open and/or close a water flow control valve). In commercial applications, for example, the initialization process results in the powering-up of a relatively large number of remote irrigation devices, in some cases, from 20-800 remote irrigation devices. If all of the remote irrigation devices are powered-up at or about the same time, the in-rush current causes a power spike at the interface controller providing the necessary current.